The present invention relates to radio communication and more precisely to a method for allocating resources in the uplink of a wireless communication network supporting real-time packet data services.
In wireless communication networks, resource allocation for traffic data may be performed by a centralized resource allocation module. This is especially the case in GPRS (General Packet Data Services) or EDGE (Enhanced Data rate for GSM Evolution) networks.
Usually, a radio terminal which has traffic data to send requires the allocation of resources to the centralized resource allocation module. The latter, by taking into account a plurality of resource allocation requests from different mobile users and specific parameters contained in the resource allocation request message (i.e. user type) allocates resources to the mobile users.
The general term resources should be understood in the framework of the present invention as radio resources i.e. either a frequency channel and/or a time slot of a frame that is/are reserved for a radio terminal to communicate with the wireless radio network. Frequency channels, respectively time slots, are usually resources used in FDMA, respectively TDMA networks. A resource can be a code in CDMA networks, it may also be a combination of frequency channel, time slot and code.
The present invention deals especially with packet-oriented wireless communication networks which support real-time data services. Such real time data services may consist in the transmission of packetized voice or video. Such real-time data services require that the transmission delay and the delay between the reception of two consecutive data frames are bounded for ensuring an acceptable quality of service. These strict requirements are sometimes difficult to fulfill since the resource allocation module cannot react as fast as necessary on each resource allocation request message.
Moreover, if the wireless communication network supports simultaneously real-time and non real time data services, the resource allocation module is even more demanded.
Several solutions can improve the resource allocation mechanism in wireless communication networks supporting real-time data services.
For example, a combination of circuit-oriented resource allocation and packet-oriented resource allocation helps the real-time requirements to be fulfilled. Upon reception of a resource allocation request message from a radio terminal having real-time data to transmit, the resource allocation module grants resources for a predefine time period or for a predefined number of real-time data frames.
A such mechanism is, for example, described in the ETSI standard GSM 04.60 and implemented by means of Temporary Block Flow (TBF). A temporary block flow is a physical connection between a transmitter and a receiver of the wireless communication network supporting the unidirectional transfer of a predefined number of layer-2 frames on traffic channels. A TBF is opened by the resource allocation module upon receipt of a “packet channel request” message from a radio terminal. Before the termination of the TBF, the radio terminal may send a further “packet channel request message if further layer-2 frames should be transmitted. In such a case, the resource allocation can be performed right on time so that there is no delay between the termination of one TBF and the opening of a further TBF.
A further mechanism is provided for in order to better estimate when a TBF should terminate and then further optimize the resource allocation. This mechanism, called countdown procedure, consists in indicating in a field of the header of each layer-2 frame, short before the termination of the TBF the exact number of layer-2 frames, the countdown value, which remain to be sent before the termination of the TBF. The countdown value is decremented each time a new frame is transmitted on the radio interface.
The countdown procedure is especially appropriate for acknowledged non-real time packet data service where lost or badly received frames are retransmitted. When a frame has to be retransmitted, the countdown value is not decremented. The transmitter alone knows if a frame is retransmitted and informs the resource allocation module of such a situation by not decreasing the countdown value.
On the contrary, the unacknowledged mode is used for real-time packet data services i.e. lost or badly received frames are not retransmitted at the initiative of the layer 2 protocol in order not to delay the whole transmission by retransmitting frames. The correction or compensation of lost or badly received frames is dealt with at higher protocol levels. To this extend the countdown procedure does not improve the resource allocation for real time packet data services.
A particular object of the present invention is to provide a method for optimizing the resource allocation procedure for real-time packet data services.
Another object of the invention is to provide a radio terminal and a resource allocation module implementing a such method.